One of science's most puzzling mysteries - the disappearance of the Neanderthals - may have been solved. Modern humans ate them, says a leading fossil expert.

The controversial suggestion follows publication of a study in the Journal of Anthropological Sciences about a Neanderthal jawbone apparently butchered by modern humans. Now the leader of the research team says he believes the flesh had been eaten by humans, while its teeth may have been used to make a necklace.

Fernando Rozzi, of Paris's Centre National de la Récherche Scientifique, said the jawbone had probably been cut into to remove flesh, including the tongue. Crucially, the butchery was similar to that used by humans to cut up deer carcass in the early Stone Age. "Neanderthals met a violent end at our hands and in some cases we ate them," Rozzi said.

The idea will provoke considerable opposition from scientists who believe Neanderthals disappeared for reasons that did not involve violence. Neanderthals were a sturdy species who evolved in Europe 300,000 years ago, made complex stone tools and survived several ice ages before they disappeared 30,000 years ago - just as modern human beings arrived in Europe from Africa.

Some researchers believe Neanderthals may have failed to compete effectively with Homo sapiens for resources, or were more susceptible to the impact of climate change. But others believe our interactions were violent and terminal for the Neanderthals. According to Rozzi, the discovery at Les Rois in south-west France provides compelling support for that argument.

Previous excavations revealed bones that were thought to be exclusively human. But Rozzi's team re-examined them and found one they concluded was Neanderthal. Importantly, it was covered in cut marks similar to those left behind when flesh is stripped from deer and other animals using stone tools.

Rozzi believes the jawbone provides crucial evidence that humans attacked Neanderthals, and sometimes killed them, bringing back their bodies to caves to eat or to use their skulls or teeth as trophies. "For years, people have tried to hide away from the evidence of cannibalism, but I think we have to accept it took place," he added.

But not every team member agrees. "One set of cut marks does not make a complete case for cannibalism," said Francesco d'Errico, of the Institute of Prehistory in Bordeaux. It was also possible that the jawbone had been found by humans and its teeth used to make a necklace, he said.

"This is a very important investigation," said Professor Chris Stringer, of the Natural History Museum, London. "We do need more evidence, but this could indicate modern humans and Neanderthals were living in the same area of Europe at the same time, that they were interacting, and that some of these interactions may have been hostile.

"This does not prove we systematically eradicated the Neanderthals or that we regularly ate their flesh. But it does add to the evidence that competition from modern humans probably contributed to Neanderthal extinction."